INFOMAR Survey CV13_01
Monday
22nd April saw the commencement of the first RV Celtic Voyager INFOMAR survey leg of
2013, named CV13_01. Operations commenced off the Cork coast
between Ballycotton and Youghal, shoreward of coverage attained in previous years. The area forms part of the South Priority Area
(SPA), stretching from Mizen Head in the south-west to Carnsore Point in the
north-east. The Priority Bays of Youghal
and Dungarvan were also partially surveyed. Figure 1 shows the extent of
multibeam coverage achieved in the area while figures 2, 3 and 4 show
detailed seabed morphologies of the bays of Ballycotton, Dungarvan and Youghal respectively.
Figure
1: Multibeam inshore survey coverage between Ballycotton and Dungarvan.
Figure
2: Seabed geomorphology offshore Ballycotton.
Figure
3: Seabed geomorphology offshore Dungarvan.
Figure
4: Seabed geomorphology offshore Youghal.
Survey
operations alternated between the inshore area above and an offshore block
south of Waterford, shown in figure 5. The offshore survey block covers an area
of approximately 320 km2. Water depths range from 50 m to
80 m approximately with depths increasing from north to south. The seabed is
mostly covered by sediment but outcropping rocks are also found in
the north.
Figure
5: Offshore survey block south of Waterford.
An
area east of Wexford and west of the Blackwater Bank was also mapped during a
period of strong westerly winds. The multibeam shaded relief image in figure 6
shows that the seabed is largely composed of sediment waves. Water depths vary
from 10 to 25 m approximately.
Figure 6: Multibeam image near Blackwater Bank Wexford.
Survey
operations moved west for the final week of survey. The area included the waters around Old
Head of Kinsale and Courtmacsherry Bay (figure 7). Its offshore extent was along
the SPA boundary, more than 12 km offshore of the Old Head of Kinsale. Water depths
ranged from 12 m to 100 m approximately. The extent of the mapped area was
approximately 400 km2. Several magnetic anomalies were observed,
attributed to the geology. Survey operations finished on 31st May.
The Celtic Voyager remained operational for over 70% of the total time.
Figure
7: Multibeam image of Courtmacsherry Bay and Offshore Kinsale.
Wrecks
A
total of 21 wrecks were mapped during this leg. Figure 8 shows an image
of a wreck off the Waterford coast. The wrecks were initially identified from
the main survey lines and then mapped in detail using a standard box in process
of three parallel lines and one perpendicular line with multibeam water column data and magnetometer data acquired on each line.
Figure
8: Multibeam image of mapped wreck.
Groundtruthing stations
In
total 128 groundtruthing stations were visited. A total of 111 samples were
acquired from these stations, with no returns at 17. A Shipek grab was used
throughout. Each sample was photographed and described. Samples varied from mud
through to gravel. Figure 9 shows a photograph of the sample obtained at station
4.
Figure
9: Shipek Grab sample photograph.
Figure
10 is a distribution plot of the visited groundtruthing stations. Each red X
marks a station.
Figure
10: Groundtruthing spatial distribution plot.
Sub Bottom Profiler Data
Sub
bottom profiler data was acquired on each survey line. Figure 11 below shows an
example of sub bottom profiler data with a palaeochannel in the view. Each
horizontal red line represents 8 metres depth. The vertical blue lines are
approximately 120 metres apart. The horizontal line near the top of the image
represents the seabed return.
Figure
11: Sub-Bottom-Profiler data example.
